Dinosaur extinction: more whimper than bang

By AAP with AG staff 2 May 2012
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Dinosaurs were already in decline before an asteroid impact, new research suggests.

DINOSAURS MAY HAVE DIED out with a whimper rather than a bang from a massive asteroid striking the Earth, scientists believe.

New research suggests different groups of dinosaurs were declining at different rates before the impact. It indicates that the creatures were not all suddenly snuffed out at the height of their reign 65 million years ago.

Some large-bodied plant eaters had already started to disappear over the last 12 million years of the Cretaceous Period. They included the ‘duck-billed’ hadrosaurs and horned rhino-like ceratopsids. Predators such as Tyrannosaurus rex, small herbivores and enormous sauropod plant eaters remained relatively stable or even became more diverse.

Dinosaurs already in decline

“Contrary to how things are often perceived, the Late Cretaceous wasn’t a static ‘lost world’ that was violently interrupted by an asteroid impact,” said researcher Steve Brusatte, from Columbia University in New York. “Some dinosaurs were undergoing dramatic changes during this time, and the large herbivores seem to have been mired in a long-term decline, at least in North America.”

There is no way to tell if a declining dinosaur group would have survived if the asteroid had not struck, said the scientists writing in the journal Nature Communications.

The researchers came to their conclusions after studying fossil evidence of biodiversity in seven major dinosaur groups.

Dinosaur extinction “complex”

“Few issues in the history of palaeontology have fuelled as much research and popular fascination as the extinction of non-avian dinosaurs,” said Steve. “Did sudden volcanic eruptions or an asteroid impact strike down dinosaurs during their prime? We found that it was probably much more complex than that, and maybe not the sudden catastrophe that is often portrayed.”

Richard Butler, a palaeontologist at the Ludwig Maximilian University of Munich in Germany, said: “People often think of dinosaurs as being monolithic. We say ‘the dinosaurs did this, and the dinosaurs did that’. But dinosaurs were hugely diverse.”

“There were hundreds of species living in the Late Cretaceous, and these differed enormously in diet, shape, and size. Different groups were probably evolving in different ways and the results of our study show that very clearly,” he says.